This invention relates to a speech synthesizer capable of electronically synthesizing human speech from digital speech data, and more particularly to a speech synthesizer module implemented in integrated circuitry and operably coupled to a commercial or home-type computer to provide speech capability therefor.
Speech synthesizers are known in the prior art. Examples of previously known speech synthesizers are disclosed in U.S. Pat. Nos. 3,803,358 and 4,092,495 and U.S. patent application Ser. No. 901,393 filed Apr. 28, 1978, now U.S. Pat. No. 4,209,836 issued June 24, 1980.
Disclosed herein is a speech synthesizer which utilizes several integrated circuits in the construction thereof. The integrated circuits include a Speech Synthesizer Processor and two Read-Only-Memories, and are discussed in detail herein.
Preferably, the aforementioned speech synthesizer is implemented utilizing standard field effect transistor, large scale integration techniques, such as P-channel MOS. Additionally, it is preferable that the speech synthesizer be compatible with control circuitry as it exists in various electronic devices.
The speech synthesizer is intended to be operably coupled in module form to a home-type computer to provide speech capability therefor, wherein the speech synthesizer electronically synthesizes human speech from coded speech data including parameters which may be stored in a suitable memory. However, the speech synthesizer may be employed in any application in which an audible verbal informational or instructional response is desired.
It was, therefore, one object of this invention that a speech synthesizer be implemented utilizing low cost, large scale integrated circuit devices.
It was another object of this invention that the speech synthesizer be electrically compatible with existing TTL logic levels.
It was yet another object of this invention that the speech synthesizer utilize coded speech parameters stored in a solid state memory.
It was yet another object of this invention that the speech synthesizer also be able to utilize coded speech parameters inputted via a control device.
The foregoing objects are achieved as is now described. A speech synthesizer is controlled by an appropriately programmed microprocessor, preferably the central processing unit of a commercial or home-type computer. The speech synthesizer utilizes data coding and compression schemes to minimize required data rates. The coded speech parameters are utilized to control the reflection coefficients of a digital filter within the speech synthesizer. The output of the digital filter is applied to a digital-to-analog converter which transforms the digital output of the digital filter to an audio signal. The reconstructed audio signal may then be utilized as the input to a conventional amplifier and speaker system.
In a specific aspect of the invention, the speech synthesizer is in the form of a module operably coupled to a home-type computer, wherein the speech synthesizer provides analog signals representative of human speech from coded digital speech data including parameters as stored either in a solid state memory on a permanent basis or alternatively as temporarily stored in another memory. In the latter instance, the coded digital speech data is made available from an external source, such as the central processing unit of the home-type computer. Thus, the speech synthesizer possesses two alternative modes of operation: (1) a "speak mode" which uses coded speech parameters permanently contained in a read-only-memory of the speech module; and (2) a "speak external mode" in which the coded speech parameters are provided from the central processing unit of the home-type computer, wherein coded speech parameters are input via an input buffer to the speech module where they are decoded and used to produce synthesized human speech. The speech module includes a speech synthesizer processor for converting coded speech data into digital speech signals in combination with a mode selector means which selectively applies either the coded speech data from the read-only-memory within the speech module or the coded speech data obtained from the external source to the speech synthesizer processor in response to a control signal provided by the external source. Such an arrangement greatly expands the library of words available to the speech synthesizer because of the vastly greater memory storage capacity afforded by the external source.